The present invention relates more particularly to the devices for separating cleaning bodies from the fluid which transports the cleaning bodies after they exit from the tubes, particularly where the cleaning bodies are recycled back to the inputs of the tubes. These devices comprise two successive separator stages with a grid or the like mounted in a section of the output duct of the exchanger and a collector connected to the outlet of the second separator stage and arranged so as to receive the cleaning bodies separated from the main current of the fluid and to remove them from the duct. The collector is generally formed by the suction nozzle(s) of a recycling pump.
The two separator stages are intended to gather together the cleaning bodies along respectively two transverse directions X and Y, perpendicular to each other, of the duct section in question which has a longitudinal axis Z.
The first of these stages, or upstream stage, comprises at least one grid formed of parallel equidistant bars whose spacing apart is less than the smallest overall dimension of the cleaning bodies, this grid being mounted obliquely across the duct section in question with its bars parallel to the plane containing the direction X and the axis Z of this section, such that the fluid flows through said grid but the cleaning bodies are stopped by it and are guided along its bars as far as its downstream end while being deviated or deflected thereby in direction X.
The second stage, or downstream stage, is in the general form of a relatively flat hopper converging in the downstream direction and in direction Y, which hopper is mounted so as to receive the cleaning bodies coming from the downstream end of the first stage, the cross section of this hopper being elongate in direction Y, at least one of its walls extending in this direction Y being permeable to the fluid but not to the cleaning bodies and at least one of its walls extending parallel to direction X forming a deflector adapted to deflect the cleaning bodies in direction Y as far as the downstream collector.
The two separator stages which have just been defined may be clearly distinct from each other.
But they may also merge with each other continuously, the permeable wall of the hopper which forms the second stage being for example formed by the downstream extension of a grid forming the first stage, this extension being possibly even connected to the rest of the grid by a curved zone free of sharp angles.
When the fluid flowing through the separation devices contains a large number of impurities, (such as shells, wood debris and the like) having dimensions close to those of the cleaning bodies, these impurities, which are directed along with the cleaning bodies by the grid of the first stage into the hopper of the second stage may, under certain conditions, collection the permeable wall of this hopper and clog it up.
This clogging reduces the fluid flow through said wall, which reduces correspondingly the force sucking the cleaning bodies into the hopper in the direction of the collector.
This reduction in fluid flow may end up as a complete stoppage of the flow and in the accumulation of the cleaning bodies upstream of said hopper or at least upstream of said collector, which defeats the purpose of the desired separation.
It so happens in fact that the normal flow of the fluid through the permeable wall of the hopper exercises a preponderant role for carrying these bodies towards the collector, the flow in question being higher than the residual flow of the fluid which accompanies the cleaning bodies into the collector, the first being of the order of 20 times higher than the second.
To overcome this serious drawback, it has already been proposed to clean the permeable wall of the hopper periodically, more particularly by temporarily reversing the direction of fluid flow through this wall.